We propose to define the subclass and allotype of IgG allo and autoantibodies encountered in the practice of blood transfusion and correlate that data with available clinical data and in vitro measures of erythrophagocytosis using a mononuclear effector cell assay which has been previously characterized. Prospective studies in the immune response are difficult. Therefore, a study on the response to 1 ug of S. Adelaide flagellin was undertaken in collaboration with S. Whittingham. The results indicate the Gm phenotype is a significant parameter in determining the IgG response to flagellin as is sex- and HLA-B locus-associated antigens. This now has to be tested on the response to erythrocyte antigens.